package day6;

import java.util.Scanner;

// https://www.nowcoder.com/practice/1183548cd48446b38da501e58d5944eb?tpId=122&tqId=33662&ru=/exam/oj
public class code2 {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        int w = scanner.nextInt(); // 长
        int h = scanner.nextInt(); // 宽
        int count = 0;
        int[][] table = new int[h][w];
        for (int i = 0;i < h;i++) {
            for (int j = 0;j < w;j++) {
                if(table[i][j] == 0) {
                    count++;
                    if(i + 2 < h) {
                        table[i+2][j] = 1;
                    }
                    if(j + 2 < w) {
                        table[i][j+2] = 1;
                    }
                }
            }
        }
        System.out.println(count);
    }
}
